Felbamate (2-phenyl-1,3-propanediol dicarbamate) is an anticonvulsant used in the treatment of epilepsy, as described in U.S. Pat. Nos. 4,978,680 and 5,082,861, which are incorporated by reference. Several syntheses of felbamate have been described, including the methods of U.S. Pat. Nos. 4,868,327, 4,982,016, 5,091,595 and 5,500,484, as well as WO 94/06737 and WO 94/27941, all of which are incorporated by reference. WO 94/06737 and WO 94/27941 teach a felbamate synthesis by reaction of 2-phenyl-1,3-propanediol with chlorosulfonyl isocyanate. This method is typical of those used to manufacture felbamate commercially.
However, a disadvantage of these processes is the production of felbamate with relatively high level of impurity. Because the average daily dosage of felbamate is about 600 mg, it is essential to control the formation of impurities in felbamate. Another disadvantage of process disclosed in WO 94/06737 and WO 94/27941 is that the process yields felbamate with a relatively low tapped bulk density, resulting in handling difficulties during processing and use. A material with a higher tapped bulk density is desirable during the manufacture of pharmaceuticals containing felbamate, particularly oral dosage forms. The oral suspension dosage form of felbamate, when made with felbamate of low bulk density, is very thick and difficult to deliver in desired administration. However, according to the present invention, the oral suspension dosage form of felbamate made with high bulk density felbamate obtained by the process of this invention is found to be free flowing and suitable for delivering the desired dosage administration.